Our great room, dining and foyer are 12' ceilings and the remainder of the first floor is 9' while the second floor has 8' ceilings. Not uncommon to have various heights

Like jdubb, we have higher ceilings in one area (living room) and 9' on the remained of the downstairs. I love it.

It's highly recommended by Sarah Susanka (Not So Big House). Especially if it's "open concept" (a highly overused term), different ceiling heights help define "rooms" where there are no walls.

Keep in mind, though, if you're changing the ceiling height by having a separate joist system in one area, so the 2nd level floor moves up where the 1st level ceiling moves up, it adds a big cost to the build. A more economic solution is to have one level of joists, and add a dropped ceiling where you want the ceiling lower. The lumber to support the ceiling is cheaper than adding in extra beams and engineering to support different floor levels.

Also. lower ceilings on upper floors has been common as long as people have been building 2 story houses. Private, family areas tend not to be as grand as more formal, public areas. You want to impress people where you can, and then save money where nobody will ever see it. This attitude is changing slightly, though. Personally, I'd rather have a house that's comfortable for ME, not built to impress strangers. But yes, it's absolutely acceptable to have higher ceilings on the main level than on the 2nd level.